1. Field of the Invention
The present invention relates to lighting fixtures and more specifically, to a lighting lamp, which uses a polygonal light guide board with an umbrella surface-like reflective layer to guide light from LEDs so as to provide a uniform lighting effect having an enhanced brightness without multi-image and flashing and to simulate the lighting effect of a ball lamp.
2. Description of the Related Art
LEDs (light emitting diodes) have been intensively used in lighting fixtures to substitute for conventional lamp bulbs and tubes for the advantages of small size, quick reaction time, low attenuation, hard surface structure, shock resistance, full-color emission (including invisible light), directional design applicability, low voltage, low current, low conversion loss, low radiation heat, easy mass production, and environmental protection. Following fast growth of market demand, blue, new fabrication techniques for white and high brightness LEDs have been continuously developed.
Many experts in different countries issued reports that declare the possibility of the application of LED techniques for regular illumination. Using LEDs to replace conventional lamp bulbs and lamp tubes for home use can save the power capacity of one nuclear plant in a country. Every country around the world invests manpower and capital to promote the development of LED technology. It has become an internal competition in development of LED technology.
However, LEDs may be too dim in bright light situations because of its unidirectional lighting feature. Therefore, a LED lighting fixture has the drawback of limited angle of illumination. To overcome this problem, multiple LEDs may be arranged together and set in different angles. However, this arrangement greatly complicates the fabrication of the lighting fixture and will also increase the cost. Further, a lighting fixture constructed according to this arrangement may produce multiple images, not practical to substitute for conventional daylight lamps.
Taiwan Patent Publication No. M306666 discloses a light guide structure for lighting lamp, which is an invention of the present inventor. According to this design, the light guide structure comprises a light guide board made of a transmissive material having a clear transmissive layer, and a reflective layer covered on the back side of the light guide board. The reflective layer has an arched convex portion on the middle (see claim 7). The light guide structure is used with a lateral light source to construct a lighting lamp that increases the angle of illumination, provides a uniform lighting effect with enhanced brightness, and eliminates the multi-image and flashing problems of conventional daylight lamps.
Taiwan Patent Publication No. M317546 discloses an improved structure of lighting fixture, which is an invention of the present inventor. According to this design, the lighting fixture comprises a lamp case, a plurality of LEDs mounted in the lamp case and adapted to emit light toward the center of the lamp case, a see-through window at the bottom side of the lamp case, a reflective board mounted inside the lamp case corresponding to the see-through window. The reflective board has a double-beveled edge at each end. When the LEDs are emitting light, light rays are well dispersed subject to the effect of the reflective board, providing stable illumination and eliminating the problem of multiple-image.
However, the aforesaid two prior art designs are functional, however they are simply suitable for bar illumination, not practical for use as a circular ceiling lamp or ball lamp.